1. Field of the Invention
The present invention relates to defoaming compositions and methods, and more particularly, to such compositions and methods for preventing the formation of foam or breaking foam in well treating fluids.
2. Description of the Prior Art
Defoaming compositions and agents have long been used in the oil and gas industry to pregnant the formation of a foam or to destroy a previously formed foam. The defoaming compositions are commonly utilized as components in well treating fluids to prevent the formation of foam during the preparation and/or pumping of the treating fluids. Also, defoaming compositions have been utilized heretofore for breaking previously formed foamed well treating fluids. That is, when a stable foamed well treating fluid must be disposed of on the surface, a defoaming composition is added to the fluid to destroy the foam whereby the non-foamed components of the treating fluid can be readily disposed of.
A variety of defoaming compositions and agents have been utilized heretofore. Examples of such defoaming compositions and agents utilized in well treatment fluids include tributyl phosphate and acetylenic diol which are environmentally unsafe. Other prior art defoaming agents which are environmentally safe include polypropylene glycol and a mixture of polypropylene glycol with a copolymer of ethylene oxide and propylene oxide monomers. While these defoamers function adequately to prevent the formation of foam in well treating fluids when they are prepared and pumped, they do not function adequately for defoaming previously formed foamed well treating fluids, and particularly, previously formed foamed well cement slurries.
Thus, there is a continuing need for improved environmentally safe defoaming compositions for use in various fluids including well treatment fluids.